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Micro-sleep: the shortest danger on the road
To learn more about the dangers of drowsy driving, we talked to two pretty alert sleep experts.July 28, 2015
Mr. Popp, Mr. Kubitzki, so what exactly is “micro-sleep”?
Popp: We sleep specialists talk about so-called micro-sleep episodes, which we monitor in our sleep laboratory. The episodes can be very brief, but may also last for 10 to 15 seconds or even longer. And it's not always necessarily the case that your eyes are closed. The condition of sleepiness or fatigue is different for every person.
Kubitzki: The term micro-sleep suggests to some: "Oh well, the danger doesn't last long." However, at a certain level of fatigue you're simply no longer capable of completely concentrating on the task of driving. And if you should nod off for one or two seconds, the minutes before and after – actually, the whole trip, in fact – are also dangerous.
I must confess that I always have a can of energy drink in my glove box. Does it help?
Kubitzki: If you ask yourself during a journey what you can do when you get tired, I must honestly say that something has already gone wrong beforehand. This also applies if you rely on technical systems; these are at best emergency solutions.
Popp: The best cure for tiredness is in fact sleep – but please not behind the steering wheel, use a rest area instead! A “turbo sleep”, as the Swiss call it, lasting for 20 or 30 minutes
really helps. But it shouldn't go longer, otherwise your circulatory system will slow down, bringing you into deeper states of sleep. If you drink one or two coffees before your nap, this will even increase the caffeine's effect, as it takes 20 or 30 minutes for it to be absorbed in the bloodstream.
Turning up the radio, rolling down the window...
Popp: Neither works, as investigations in driving simulators and on the road have shown. On the contrary: If you subjectively feel more awake when there's loud music or cooler air –which objectively is not true – then you're underestimating the degree of your tiredness as well.
Auto manufacturers are offering warning or correction devices against micro-sleep. Do they help?
Kubitzki: It's a contradiction in terms if I expect a vehicle to reliably warn me against driving a vehicle! No system is able to predict the moment you actually fall asleep. It's possible to recognize typical change patterns via certain parameters such as steering behavior or track measurements, and on this basis send out warning signals to the driver. And this is something that the various “driver drowsiness detection systems” of auto manufacturers are already doing.
But we lack the appropriate data to be able tell how whether all these systems are really capable of reducing the number of accidents caused by tiredness. And for as long as these data are missing, the assistance systems such as the lane departure or distance warning system, the emergency braking system and others, are merely a pragmatic approach. But let me say it again: when it comes to errors caused by tiredness, they are at best emergency solutions!
Popp: The driver drowsiness systems are based on global fatigue indicators. But there are major differences from driver to driver. The effect that fatigue has on driver behavior, eyelid closure, etc. diverges too much for us to be able to come to generally valid conclusions.
Everyone is tired in his own way, so to speak.
Popp: Exactly. For this reason it's important to have different measures to counter tiredness at the steering wheel. One example are "rumble strips" which indicate via vibrations or sound whenever someone crosses the median or hard shoulder. And there is a need for a sufficient number of rest and parking areas. Truck drivers who notice that they're getting tired often can't even find a place to take a break, because all the rest areas are full.
Another possibility would be architectural or colorful design measures for particularly monotonous stretches of road, so that there is always something to see. The most important thing, however, is that people with chronic fatigue symptoms have themselves medically examined and treated!
Can we at least place our hopes in the Google car? There you will hopefully always have plenty to see.
Kubitzki: From an accident research point of view I've got very mixed feelings. In general, technology always makes driving easier. A car in the luxury segment today already offers numerous driver support systems. And when we talk about autonomous driving, the question arises, particularly in the world of work: Who does the gained time belong to? If, for example, a truck driver drives in the autonomous mode, is that recognized as driving time or rest period? Is it working time or maybe even private time? Does he then have to, or is he able to, use it for regenerating himself? Or is he obliged to do other things during this time, which in turn prevent regeneration and increase tiredness?
Popp: The aircraft pilot in the cockpit must also be able to intervene and react at any time, even if the aircraft is in the auto-pilot mode. However, if I had nodded off in the car, it may take too long for me to get out of my state of sleep inertia and really become able to react again.
When I drive home again after our discussion, what percentage of fellow road users will really be wide awake?
Kubitzki: The post-lunch low should already be over – but I wouldn't bet my life on it …
Popp: Naturally it also always depends on how much sleep people got throughout the whole week. Additional sleep pressure builds up at the end of the week. You can witness this very well in the underground in Japan, for example. But it's Wednesday today, the weekend is still some time off.....
Kubitzki: For many decades now, accidents have been peaking twice a day: first when people drive to work, and then again when they drive home after work. When we finish work and drive home after this discussion, the probability of having an accident is higher. However, if we wait in the cafeteria until 7.00 pm, peak hour traffic will have eased off and the accident risk will be lower.
But let's be frank: as respected men in this field, what personal suggestions do you have to prevent micro-sleep?
Kubitzki: Luckily I've never been in the situation of having to make really long car journeys or feeling that I'm no longer capable of driving. But I'd rather take too many breaks than too few, even if I think I don't need them.
Popp: My personal tactic for if it turns out to be a longer drive and it’s getting late: take a short nap in between and drink some green tea out of a thermos.
This interview originally appeared in 1890, the customer magazine of Allianz Germany (in German language only).